1. Field of the Invention
The present invention relates to a storage managing system, a storage managing apparatus, and a storage managing method for managing data storage of a storage medium.
2. Description of the Related Art
Various detachable storage media are used, as storage devices for storing files, in personal computers, personal digital assistants (PDA), portable phones, digital still cameras and the like.
This kind of storage media cannot physically protect data stored therein, unlike a storage device that allows writing of data only one time, such as a compact disc-recordable (CD-R) being used for only one burning of data thereon. Thus, each user must be careful about protection of the stored data. More specifically, even when the data of a storage medium that is in a readable/writable condition can be managed and protected by specific software (e.g., a file system or the like), it is possible to cancel the protection applied to the data of this storage medium when other software is used for rewriting or deleting of data. Furthermore, the data managing software is determined depending on an apparatus receiving a storage medium. In this respect, the protecting method dependent on the type of software cannot assure reliable protection of the stored data. Furthermore, in any storage medium, all of the stored data is completely deleted when the storage medium is formatted.
However, it is a recent trend that advanced storage media have the capability of protecting stored data. For example, a Secure Digital (SD) memory card is a typical storage medium that has an entire write protect function for applying write protection to the entire data region of the storage medium. More specifically, the SD memory card is equipped with a special switch on its side surface to select either write protect ON or write protect OFF. When the write protect ON is selected, all of the data stored in the SD memory card is write protected. Furthermore, the SD memory card has a partial write protect function for applying write protection to a limited portion of the data region of the storage medium.
For example, the data region is divided into a plurality of units, which are generally referred to as WP blocks, each having a data size of, for example, 2 KB. The SD memory card, if it has the above partial write protect function, can apply write protection to each WP block. Japanese Patent Application Laid-open No. 2001-188701 discloses a technique for managing, for each cluster, deletion of stored data.
However, according to the above-described entire write protect function, the SD memory card is always required to apply write protection to the entire data region of the storage medium even when the write protection is required for only one file. This is very inefficient and inconvenient.
Furthermore, according to the above-described partial write protect function, usage of the data region will be inefficient unless the head of a file matches with the head of a WP block. Furthermore, in a case where data is stored in accordance with a file allocation table (FAT) file system, a file may be divided into clusters and file data may be separately stored in non-consecutive regions. Therefore, if a FAT or a directory entry, which is required to identify the position of each file, is changed by formatting or updating of the FAT, it will be impossible to restore the file.